Indoor Air Quality – When Should You Test?


Often clients want to have their facilities "tested" for "bad indoor air quality". However, testing the air is usually not the best first step that a responsible occupational hygienist should take. A great deal of thought should be given to the problem before testing the air.


Indoor Air QualityFirst, Identify the Problem

If you don’t really know what the problem is then how do you know what to look for? Some typical problems include:

  • One area is always stuffy and lots of employees in that area have frequent headaches, eye, nose and throat irritation, and fatigue that go away when they leave the building.
  • It's cold in one area and hot in another.
  • There is a strong chemical smell in the areas surrounding the storeroom.
  • The employees in one specific room complain of late afternoon headaches almost every day.
  • There is a mouldy smell in the basement, and there are moisture stains on the walls, ceiling or floor. The supervisor has only been there a couple of years and has recently been diagnosed with asthma. A number of known asthmatics state that they have to use their inhalers more often when they spend time in the basement.


All of these problems require different approaches in order to solve them. Testing the air should not be the first step in any of them.

There are no appropriate standards

There are no appropriate standards for indoor air quality in environments such as offices and general buildings.

  • There are industrial standards for exposure to some chemicals used in manufacturing and other workplace settings. These are not suitable for offices or commercial buildings, and they should never be used in residential settings.
  • There are no standards for indoor levels of moulds. Susceptibility depends on the individual health status of the exposed person and the potential danger from each particular species of mould.
  • Ventilation guidelines are not enforceable unless they are part of a building code. Newer buildings are generally designed according to newer ventilation guidelines, but older buildings would have been built to the code that was in existence at the time of construction and may now be outdated.

This lack of standards makes it difficult to interpret the results of any testing. Testing may therefore simply add to the confusion and create an air of mistrust between the occupants and the management or owners of the building.


DO NOT TEST unless you are certain that:


  • the results can be meaningfully interpreted
  • the results will add meaningful information
  • it is not being done because you can’t think of anything else to do

What is the first step in determining whether the air in an indoor area is of good environmental quality?


Check the obvious!

  • Walk through the building identifying potential problems using common sense plus your eyes and nose.
  • Look at general cleanliness (or lack of it) in each of the areas you inspect.
  • In addition to offices, common areas, storerooms, basements and lofts, also look at cleaner’s cupboards, areas that house ventilation equipment, and unused areas.
  • Ask whether new furniture, dry-walling, or fittings have recently been installed.
  • Ask whether any painting or other building maintenance has recently been carried out.
  • Note where carpeting is used. How is it cleaned, and how often? Does it ever get wet from flooding or leaks, and if so, how quickly does it dry out?
  • Walk around outside of the building and look for potential pollution sources.
  • Look for locations of fresh air intakes and exhausts. Are they too close together, allowing exhaust air to be sucked back into the building? Are the intakes located near waste bins or where buses, trucks or cars idle?

All of these things can have an impact on indoor air quality. Some additional things that should be done early on, before resorting to actually testing the air, include:

  • Examine building usage

Compare the hours the building is used with any automatic timers that may be set to turn the mechanical ventilation systems on and off, and make adjustments as necessary.

Mechanical systems should be turned on early enough in the morning to let these systems attain full capacity by the time work begins.

When activities are outside normal working hours, this must be communicated to the facilities management.

Other important steps include: a building walkthrough, taking a history of the building and any past and present maintenance problems, reviewing the history of building and the land usage on the property and surrounding neighbourhoods, a study of architectural and mechanical blueprints, interviewing the maintenance staff, and anyone else who might add information about the physical structure of the building and the activities that go on in and around it.

It is also be useful to interview the building occupants and ask for their help in identifying problem areas. Set up good lines of communication between management, staff, and other workers. This is crucial and cannot be over emphasised! Ask the company doctor or nurse if they have observed or documented an increased incidence of health complaints. A symptom survey may be considered if lots of people are affected.

  • Ask about maintenance service contracts

Building managers often have service contracts to take care of certain parts or all of the building. This is especially true for the ventilation equipment. Ask questions about how often filters are scheduled to be changed, and about what other components are included in an annual service contract (ask to see the maintenance log for proof of when this work was completed).

If the facility subcontracts out cleaning services, find out what is included in the contract. Ask about the cleaning agents used, the volumes and the frequency of use. Read the labels.


  • Plan minor renovations out-of-hours

Schedule minor jobs such as painting, floor re-surfacing or carpet installation during hours when the building is not in use.


Use low emitting paint, glues, polyurethane, and other building materials whenever possible.

  • Build communication into large renovation projects

Before any major renovation project is scheduled, meet with the contractor, building supervisor, manager, heads of departments, and the health and safety committee. Set up a plan for communicating relevant information to all employees, contract workers and other occupants.

Plan to do as much work as possible outside of normal work hours.


Seal off construction areas from non-construction areas using temporary barriers to minimize contamination in areas that will be used for normal work activities.

You may decide to call in a professional to carry out the building assessment but there are many useful things you can easily do yourself.


What you can do yourself

  • Develop proactive risk communication
  • Do routine scheduled maintenance, especially on heating, ventilation and air conditioning systems
  • Remove pollution sources
  • Substitute low emitting products whenever possible
  • Fix all leaks promptly!
  • Remove and discard all porous materials damaged by water. This includes ceiling tiles, carpets, furnishings, and even wallboard.
  • Schedule repairs/renovations out of hours


When is indoor environmental testing useful?

Indoor Air QualityWhen all of the practical steps and investigations above have been conducted and the problem has been identified, air sampling may be one of the steps necessary.

Air testing might confirm or refute a highly suspected source that is uncovered during the walkthrough inspection.

Air testing is most useful when a specific contaminant or contamination source has already been identified as a likely culprit, and quantitative data are needed to:

  • Document the degree or extent of the hazard, or
  • Document different locations in a building where elevated levels or severe conditions exist.


Air testing may also be useful in a qualitative manner when trying to differentiate between several suspect chemicals or sources.

Although air testing is sometimes useful in tracking down chemical sources, air testing for mould is a completely different scenario. The most difficult factor in interpreting air results from mould testing is that a large variety of moulds are present in our everyday environment. Most of the time, moulds normally found outdoors are also present indoors. This is because they are carried in on clothing and shoes, and also via open windows, doors, and fresh air intakes.


So, to review, indoor air testing may be useful when:

  • It is part of an overall evaluation
  • When the data is interpretable
  • When the data helps to illustrate it's place in the overall evaluation
  • NEVER alone

After undertaking the steps described above, you may find it necessary to hire one or more professionals. Remember that varied problems may require more than one type of specialist. For example, you may need a ventilation engineer, or a moisture specialist, or an architect, or an industrial hygienist, or even an environmental/ geology consultant. Some tips to follow when hiring a consultant include:

  • Discuss the problem with your company doctor or nurse and enlist their help with risk communication to all of the stakeholders. They may also be able to help you select the right kind of consultant for the job at hand.
  • Have a clear understanding of the problem, so that you can direct the consultant properly.
  • Make sure the consultant explains the scope of the project up front including what they can and cannot do. Communicate this to all of the stakeholders so people will have a realistic expectation about the process.

N.B. The expenditures and effort to prevent most indoor air quality problems is a fraction of that required to solve problems once they develop.

Adapted from “Indoor Air Quality Testing Should Not Be The First Move” by ML Heyman of the Connecticut Department of Public Health